This invention relates to a method and an apparatus for hydrolysis treatment of cellulosic fiber material.
Hydrolysis of cellulosic fiber material by means of sulphate cooking has been known for many years. Such processes have been suitable for the manufacture of high-grade dissolved pulp which is useful in the production of rayon, silk and cord. The hydrolysate liquid resulting from such conventional processes, may contain 15-20% of the dry wood substance, for example, pentosans. These dry substances tend to form scalings, so called "gunk" or "carmel," and pluggings both inside as well as outside of the reaction vessel (commonly referred to as the digester).
In discontinuous cooking processes, treatment takes place in the same digester but alternating between acid hydrolysis and then alkaline cooking. In continuous cooking processes, where each step occurs within a certain portion of the digester, the problem of scaling and pluggings within the digester is accentuated. To date, it has been customary to extract both the hydrolysate and the black liquor (formed in conventional digestion processes) together in such continuous processes for common burning.